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Obesity Linked to Coronary Calcium

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Patients who retained overall and waist fat had a greater risk of CAC and disease progression the longer they held onto those pounds.

Note that longer duration of obesity was associated with higher levels of blood pressure, glucose, insulin, C-reactive protein, HDL cholesterol, and triglycerides, as well as diabetes and use of antihypertensive and lipid-lowering drugs.

Patients who retained overall and waist fat had a greater risk of coronary artery calcification (CAC) and disease progression the longer they held onto those pounds, researchers found.

Year-over-year, the risk of CAC increased by hazard ratios of 1.02 (95% CI 1.01-1.03) and 1.03 (95% CI 1.02-1.05) among patients who maintained overall and abdominal obesity, respectively, and after adjustment for body mass index (BMI) and other confounders, according to Jared Reis, PhD, of the National Heart, Lung, and Blood Institute in Bethesda, Md., and colleagues.

Risk for progression of CAC, a a subclinical predictor of coronary heart disease, rose 4% each year a patient maintained overall and abdominal obesity (95% CI 1.01-1.06 and 95% CI 1.01-1.07) after adjustment, they wrote online in the Journal of the American Medical Association.

The authors noted that CAC builds up over time and can play a role in predicting coronary heart disease events, but prior research has not studied associations between duration of obesity and risks of coronary atherosclerosis in-depth. They cautioned that this association is important due to the doubling of obesity rates in adults and tripling of obesity rates in adolescents over the past 3 decades.

Keeping fat off may be one of the best things patients can do for their health, Rae-Ellen Kavey, MD, of the University of Rochester Medical Center in Rochester, N.Y., told MedPage Today.

“It’s important for doctors taking care of young patients to emphasize the importance of a healthy lifestyle to maintain a lower body weight for as long as possible,” she added.

The authors studied the association between duration of overall and abdominal obesity with the presence and 10-year progression of CAC, which is a predictor of coronary artery disease, in a population of 3,275 white and black adults, ages 18 to 30, at baseline. Participants did not have overall obesity or abdominal obesity at baseline as part of the Coronary Artery Risk Development in Young Adults (CARDIA) study.

Participants underwent a CT scan to to identify CAC at years 15, 20, and 25 of follow-up, while duration of overall and abdominal obesity were measured through BMI and waist circumference at years two, five, seven, 10, 15, 20, and 25. The authors defined 10-year progression of CAC as incident CAC in 2010 to 2011, or an increase in calcification score of 20 Agatston units or more.

Outcomes were calculated in two models. One was adjusted for age, sex, race, CARDIA field center, BMI or waist circumference, education, physical activity, energy intake, smoking status, and alcohol consumption. The other model adjusted for those factors as well as systolic blood pressure level, use of antihypertensive and lipid-lowering drugs, diabetes, C-reactive protein, fasting insulin, total cholesterol, HDL cholesterol, and triglycerides.

Most participants were white (54.3%), women (50.6%), and did not develop overall (59.6%) or abdominal (59%) obesity over the course of the study.

Among those who became obese, mean duration was 13.3 years and 12.2 years for overall and abdominal obesity, respectively. Initiation of obesity occurred at the mean ages of 35.4 and 37.7, respectively.

Longer duration of obesity was associated with higher levels of blood pressure, glucose, insulin, C-reactive protein, HDL cholesterol, and triglycerides, as well as diabetes and use of antihypertensive and lipid-lowering drugs.

CAC occurred in 27.5% of participants with a median score of 25 Agatston units, and presence and extent of CAC were significantly associated with duration of overall and abdominal obesity (P<0.001 for both).

Compared with those with CAC who never developed obesity, 38.2% of those with overall and 39.3% of those with abdominal obesity had CAC.

While both overall and abdominal obesity duration were significantly associated with risk of calcification and progression, these associations were attenuated after additional adjustment.

Among those who were obese the longest, there was a 54% trend for risk of CAC versus those who were obese for the shortest period of time (P=0.07), while progression was associated with a significant 99% increased risk and 2.32-fold increased risk among those with overall and abdominal obesity, respectively.

“The additional adjustment variables in the second model could be in the causal pathway between overall and abdominal obesity duration and CAC; we regarded these models as possibly explanatory,” the authors wrote.

However, they noted that the study was limited by frequency of obesity measurement, use of waist measurement for abdominal obesity, missing measurements at some follow-up years in some participants, and selection bias as the patient population was limited to those who had completed at least one coronary CT during follow-up.

The study was supported by the National Heart, Lung, and Blood Institute (NHLBI).